Windows Azure - WCF Hosting Methods

In the previous article we have experimented the ways of WCF hosting in Windows Azure. In this article I would like to summarize the important points of WCF service exposing in Windows Azure.

There are multiple ways of hosting WCF service in Windows Azure.



Let us examine them closely.



Method 1: Web Role Hosting

In the Web Role hosting, the WCF service is hosted inside IIS. This will give the advantages of IIS to the WCF service.

• Identity Management
• Recycling
• Caching
• Pooling
• Logging

The Service creation will be much easier in this method as Visual Studio provides the templates for Service (.svc files). We need to create a new .svc file and place it in the web role project. The host names and ports are configured by the deployment and we can access the service through a browser.

The metadata end points are also automatically added. This saves a lot of amount of work from the developer side.

Method 2: Worker Role Hosting

Here the developer has to perform more work in creating the service contracts by defining the attributes in the contracts and implementation.

This method is advised if more control is needed over the service. We can easily configure the protocols in this way. In this case a corporate port has to be opened to expose the service while using the worker role.

Method 3: Hosting through AppFabric

In this method the WCF service is exposed through the Service Bus service feature of Windows Azure AppFabric. We can choose this option if we need to connect two disconnected applications.

This method is self hosted and more configurations needed. Here we can connect two disconnected applications using the Service Bus namespace. The namespace identifies the subscription and will be used for billing purposes on the cloud.

The Service Bus provides the following features:

• Connectivity between disconnected applications
• Higher Availability

Relay Service

There are two modes of connectivity in the Relay Service.

• TcpRelayConnectionMode.Relayed
• TcpRelayConnectionMode.Hybrid

The default mode is Relayed and here the service and client is connected through the relayed service.

Relayed Mode Connectivity

The following picture depicts the process in the Relayed mode.

The steps involved are following:

Step 1: The WCF Service authenticates and registers with the Relayed Service using the namespace and Provider keys.

Step 2: The Client authenticates with the Relay Service

Step 3: Client invokes a method using the Relay Service

Step 4: The Relay Service redirects the call to the registered WCF service.

Hybrid Mode Connectivity

In the Hybrid way of connectivity the client can communicate directly to the service. First the client connectivity starts as Relayed as usual and then if there is possibility of connecting directly to the service it will be provided.

Summary

In this article we have discussed the various WCF exposing methods in Windows Azure like web role, worker role and through AppFabric Service Bus.